07 April 2016

If you shop for ecological food, you’re also better prepared to drive an electric hybrid car in the best possible way. But being trained in ecodriving could almost be a disadvantage, as researchers from LiU and VTI show in a study funded by the Swedish Energy Agency.

For nearly three years, researchers at Linköping University and VTI have cooperated on a research study about electric hybrid cars. In the project, driving electric hybrid cars is compared with driving cars that run on biogas or gasoline. The drivers had an opportunity to respond to surveys, and the researchers logged their driving.

Technicians and social scientists here worked side by side, and the studies have yielded a number of interesting results:
Ekologisk matkasse
The drivers use the driving style they are used to and do not make use of the advantages of the respective cars.

“In the survey responses, we see that many believe they adapt their driving style to the car, but we can’t see any trace of that in the logged driving sessions. It seems as if they continue to drive the same way they’re used to,” says Christofer Sundström, researcher at the Division of Vehicular Systems at Linköping University.

One exception

There is a thrilling exception. Among other things, the logs show how well the driver makes use of the hybrid car’s opportunities to choose the fuel. In the car, there are buttons with which the driver can select electricity, hybrid, or diesel only.

Knappar för inställning av hybriddriftPhoto credit: Monica Westman“In the driving sessions by drivers who indicated they shop for ecological food, we can see that they make active choices to get the car to run as long as possible on electricity,” Mr Sundström says.

This is something that could be due to the fact that they are conscious consumers who are interested in knowing how the car actually works.

Being interested, however, is not always enough.

“To use the battery as well as possible, you need to accelerate carefully and then brake slowly so the battery has time to charge. People trained in ecodriving have a disadvantage here,” says Lars Nielsen, professor of vehicular systems.

Gains in lower speeds

Yet another result is that the gains in energy consumption for an electric hybrid car are found in the low speeds; at high speeds the energy consumption is roughly the same regardless of which fuel the car is running on. Since the car is so stingy with its energy it could pay, for example, to run on diesel at a good but even speed on highways so as to have electricity remaining for city traffic.

The drivers in the study see both advantages and disadvantages with electric hybrid cars. They think the cars are quiet and pleasant to drive, but they think the range for electricity is too short – and in certain situations in city environments, it is so quiet that people can’t hear it coming. And so far, the electric hybrid is considered to be too expensive.

Christofer SundströmPhoto credit: Monica WestmanThe drivers of the electric hybrids also turned out to be more sensitive to actual fuel consumption than the others.

“Even if they know that cars consume more, the tolerance among electric car drivers is low. The car can’t only go thirty-five kilometers on electricity if it’s been specified to go fifty,” Mr Sundström says.

No link to their own driving

Nor do the drivers see any link to their own driving style. One clear conclusion is therefore that knowledge is needed about how the car works in order to utilize the advantages of electric hybrid technology. There may also need to be some type of cognitive support so that the driver can easily see how well the electricity is being used.

“A brief text on the dashboard or a voice that says, for example, ‘Brake more slowly so the battery can charge more energy’ would certainly help those who today believe they are adapting their driving style,” Professor Nielsen says.

He is also satisfied with the cooperation.

“The project shows the strength in cooperation between LiU and VTI. We’d never have gotten these results if we researched by ourselves.”

The “Plug-in hybrid” research project

The research concerning the behaviour of electric hybrid drivers is one of three studies that are part of the “Plug-in hybrid” project. The other studies deal with decision-making processes and with smart energy use in “Smart Post-Carbon Cities”. The research was funded by the Swedish Energy Agency.

The behavioural study consists of two parts: one in which ten people, all employed at VTI, were allowed to borrow and drive an electric hybrid car for five weeks; the requirement was that they use the car to and from work, and otherwise for free driving.

In the other study, the two electric hybrid cars in LiU’s rental fleet were studied. They were rented on a total of 256 occasions during the time the project was in progress. The drivers drive only a few times. In both studies, the drivers had an opportunity to respond to a survey, and their driving was also logged. As a comparison, corresponding investigations were also conducted with a car in LiU’s rental fleet that runs on biogas and gasoline.

At VTI, Magnus Hjälmdahl was responsible for the design and collection of surveys that were then supplemented with technical data that was analysed by researchers Christofer Sundström (LiU) and Christer Ahlström (VTI).

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